Effects of combining physical activity with psychotherapy on mental health and well-being: A systematic review

•Expands on findings from previous reviews by including adolescents, and both clinical and non-clinical populations.•Includes 22 studies conducted with 4110 participants, across a diverse range of settings.•Psychologically-informed physical activity programmes may be as effective as psychotherapy alone for improving symptoms of common mental health disorders.•No apparent dose-response relationship; further research required into potential psychosocial mechanisms of change. : Despite a vast evidence-base advocating the psychological benefits of physical activity, relatively little is understood about how combining physical activity with psychological therapies may influence these positive effects. The aim of this paper is to systematically analyse evidence from studies adopting a combined approach, and identify potential mechanisms of action on clinical outcomes. : The Embase, PsycINFO and Medline (PubMed and OVID) databases were searched for applicable trials published up to December 2018. Relevant data was extracted from eligible studies, and the Effective Public Health Practice Project (EPHPP) tool was utilised to objectively assess the quality of each study. : Twenty-two studies met the inclusion criteria, seven of which were rated as methodologically `strong'. Combining physical activity with psychological therapy consistently engendered positive effects on outcomes compared with treatment as usual. Similar improvements in psychological outcomes were observed in most (7/8) groups receiving physical activity alone. Increased levels of physical activity were observed in psychologically-informed interventions, however this effect was unrelated to changes in psychological outcomes. : Clinical and methodological heterogeneity precluded meta-analyses of results, while risk of bias detected in the studies may compromise overall validity of the findings. : Physical activity interventions may be a viable alternative to psychological therapies, provided psychological approaches are incorporated into the implementation design (i.e. behavioural activation). Improved psychological outcomes may be observed regardless of `dose' received, however further research is required to ascertain whether psychosocial mechanisms of change mediate positive effects.